Conventional cylindrical alkaline zinc-manganese dioxide cells (also known as “alkaline cells”), such as, for example, AA batteries, AAA batteries, and D batteries, employ a conventional bobbin construction containing a single anode and a single cathode. The rate capability of such conventional alkaline cells is typically limited due to a limited interfacial area existing between the anode and the cathode and excessively thick electrodes (both anode and cathode). An increase in the anode-cathode interfacial area would raise the cell's rate capability.
Battery constructions that employ multiple electrodes in order to achieve a higher interfacial area between the anode(s) and the cathode(s) are known; such designs can also use thinner electrodes. For example, one known design employs more than one anode in combination with a single cathode or more than one cathode in combination with a single anode. Conceivably, more than one electrode of both types could also be employed, in combination.
But such known designs utilizing multiple electrodes are complicated by the need to electrically interconnect several separate anode and/or cathode structures, essentially creating parallel electrical connections between the various portions of the same electrode type/polarity, i.e., anode-anode connections and cathode-cathode connections, so that these can discharge and deliver energy simultaneously.
For example, U.S. Pat. No. 5,869,205 is directed to an electrochemical cell having a first electrode, such as a cathode, and a plurality of second electrodes, such as anodes. A plurality of cavities is formed within the cathode, and a current collector electrically connects the anodes together. U.S. Pat. No. 7,341,803 is directed to an alkaline cell with improved high-rate and high-power discharge capacity, wherein the cell has an additional anode or cathode.
WO 2004/095606 A2 is directed to a cell having at least one pre-formed pellet disposed inside the cell's housing and including an outer electrode portion formed from a material to geometrically define the pellet in a solid form. The pellet includes an inner electrode encapsulated by a separator and imbedded within the material of the outer electrode portion. WO 2005/022671 A1 is directed to a cell, such as a cylindrical alkaline cell, comprising an inner electrode encapsulated by a separator and having a thin cross-section in a folded configuration, the inner electrode being formed such that its outer extent is generally conforming to a contour defined by the interior surface of the housing.
It appears that in some of the above attempts the electrode interfacial area can be increased and the effective thicknesses of both the anode and cathode electrodes can be reduced relative to those in an ordinary cylindrical alkaline cell. These approaches, however, will likely require complex and expensive manufacturing processes. The complexity and cost are born by the need to interconnect electrically the multiple anodes and multiple cathodes, the need to create non-symmetric, non-concentric shapes, and the need to isolate interconnecting means inside the cell.
There is a need, therefore, for a cell having an increased electrode interfacial area and thus providing superior high-rate performance—but not requiring the interconnection of multiple anodes and cathodes inside the cell.